1. Field of the Invention
The present invention relates to a structure of a bond pad, and more particularly to a structure of a bond pad to prevent testing probe pin contamination.
2. Description of the Prior Art
As illustrated in FIG. 1, it shows the conventional bond pad structure. A metal conductor layer 10 is formed on the substrate, and it is consisted of aluminum-copper alloy (AlCu) serving as a bond pad. Next, a titanium Nitride (TiN) layer 12, an oxide layer 14, a nitride layer 16 are subsequently deposited on the metal conductor layer 10. They serve as a passivation layer. A contact hole 18 can be formed via photolithography and etching steps to etch a portion of the titanium Nitride (TiN) layer 12, the oxide layer 14, the nitride layer 16. A testing probe pin directly contacts on the metal conductor layer 10 to measure the conductivity of the metal conductor layer 10. Because the conventional testing method uses aluminum-copper alloy (AlCu) as a top metal of bond pad which is very soft, when the testing probe pin directly contacts on the metal conductor layer to measure the conductivity of the metal conductor layer, the aluminum-copper alloy (AlCu) residue will easily reside on the probe pin head. After probing many times, the probe pin will be contaminated seriously, and the method will result in two major disadvantages as follow:
(1) Time between probe pin maintenance need to be shortened. This will increase probe pin wear out rate (i.g., the probe pin usually needs to be polished to maintain the normal testing function).
(2) It will increase overkill ratio (i.g., the probe pin is usually serious damage reduced by abnormal electrical effect on the contact surface of tested metal). Since there is aluminum-copper alloy (AlCu) residued on probe pin head, the contact resistance between the probe pin head and the bond pad will apparently increase. In some critical testing environment, such as high frequency or low supplied voltage testing, it is very easy to cause overkill. However, high frequency and low power device is the trend for future product.